Zippered film feed and stretcher for package forming

Abstract From the Canadian patent

A method and mechanism for advancing a continuous length of bag making plastic film having reclosable fastener strips extending therealong with a filling tube over which the film is formed, means for sealing the edges of the film over the filling tube, or for joining the fasteners to form bag tubing opposed, pairs of advancing belts for pressing the film against the tube and driving it incrementally downwardly. Opposed cam surfaces at each of the bag edges contact each other at a point just outside of the bag edges and progressively walk into the edge of the bag with the point of contact shifting in an outward direction while it progresses inwardly on the bag to apply the stretching force …